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One gallon of soft drink is made of 40% orange juice and 60% water, ho [#permalink]

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16 Sep 2016, 21:44

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manishtank1988 wrote:

Hello Friends, can someone please let me know what am i doing wrong?I did similar to what Senthil7 did but instead of using initially o:t = 0.4:1 i used o:t = 2/5 & finally o:t = 60:100 i used o:t = 3/5 (2+x)/(5+x) = 3/55*(2+x) = 3*(5+x)10 + 5x = 15 + 3x2x = 5x = 5/2 = 2.5Therefore, additional gallons added = 2.5 - 1 = 1.5???I know that the answer is A but i am not able to figure out what i am doing wrong? Can someone please help!!!

1 gallon contains 0.4 gallon orange juice.

The numbers you have taken: Total --> 5 gallons; Orange juice --> 2 gallons. This step is fine.'x' is the amount of orange juice added.You get x as 2.5 gallons. i.e. 2.5 gallons of orange juice is addedIf your assumption of 5 gallons corresponds to 1 then 2.5 gallons corresponds to 0.5

Re: One gallon of soft drink is made of 40% orange juice and 60% water, ho [#permalink]

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28 Aug 2017, 18:16

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HarpreetSinghBajwa wrote:

Bunuel wrote:

One gallon of soft drink is made of 40% orange juice and 60% water, how many additional gallons of orange juice must be mixed in to make the orange juice 60% of the soft drink?

A. 0.5B. 1C. 1.25D. 1.5E. 2

can someone please solve this problem with diagram?

Attachment:

newmixtureOJ.png [ 33.62 KiB | Viewed 1518 times ]

HarpreetSinghBajwa , if you are looking for an alligation diagram, you will have to look elsewhere. I do not not use the method. But alligation is a form of weighted average. I use straight weighted average, and I believe I am in the minority. I have posted links to other methods below.

In the diagram, there is an original container of Soft Drink A. Soft drink A is 40% orange juice (and 60% water, but we need to track on the concentration / percentage of orange juice - disregard the water). Volume of A is ONE gallon.

Then "juice" is added to A. That juice is 100% orange juice. The question asks us to find how many gallons of the 100% juice, which I've called B, we must add in order to end up with a NEW MIXTURE that is 60% orange juice.

The formula is in black text below the containers. "Concentration" [of orange juice] means: orange juice is 40% of A, 100% of B, and 60% of the final mixture.

We are increasing the concentration of orange juice in the final mixture. But we don't know how many gallons of pure orange juice we need to go from a concentration of 40% orange juice to 60% orange juice. So we use the formula to find out how many gallons. There are many iterations of that formula.

I'll write the equation with and without decimals. I usually use decimals for percentages (concentrations). 100% in decimal form = 1

One gallon of soft drink is made of 40% orange juice and 60% water, ho [#permalink]

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28 Aug 2017, 22:06

According to question after adding extra orange juice the water content is 40% of new quantity.Original water content = 60% of 1 = 0.6Using option ANew quantity is 1+0.5 = 1.5 Water content in new quantity is 40% of 1.5 = 0.6 which is the water content originally available.Thus option A_________________

One gallon of soft drink is made of 40% orange juice and 60% water, ho [#permalink]

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28 Sep 2017, 16:14

genxer123 wrote:

HarpreetSinghBajwa wrote:

... if you are looking for an alligation diagram, you will have to look elsewhere. I do not not use the method. But alligation is a form of weighted average. I use straight weighted average, and I believe I am in the minority. ...

genxer123 - Very nicely done! I am starting to like weighted averages method as well. IMO, it is a fail safe method compared to Alligation, which is only applicable when the resultant mixture's information is given (e.g., ratio or volume).

p.s. On a side note, why does M$oft draw a red squiggly under the word Alligation? It seems to be a correct spelling

Last edited by Blackbox on 28 Sep 2017, 21:40, edited 1 time in total.

One gallon of soft drink is made of 40% orange juice and 60% water, ho [#permalink]

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28 Sep 2017, 18:56

Blackbox wrote:

genxer123 wrote:

HarpreetSinghBajwa wrote:

... if you are looking for an alligation diagram, you will have to look elsewhere. I do not not use the method. But alligation is a form of weighted average. I use straight weighted average, and I believe I am in the minority. ...

genxer123 - Very nicely done! I am starting to like weighted averages method as well. IMO, it is a fail safe method compared to Alligation, which is only applicable when the resultant mixture's information is given (e.g., ration or volume).

p.s. On a side note, why does M$oft draw a red squiggly under the word Alligation? It seems to be a correct spelling

Re: One gallon of soft drink is made of 40% orange juice and 60% water, ho [#permalink]

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28 Sep 2017, 21:38

genxer123 wrote:

... I gave alligation a very determined try. I know it helps many. Alligation lost me somewhere near the "numbers play tug of war backwards" analogy.

I learned the weighted average method for the GRE. For me, it is quick and accurate ...

I agree. Well, to me, alligation method is not the savior of the day but it is good to know as a fallback plan and I meant to say "ratio" not ration in my earlier post :D

Weighted Avg. is still new to me and I am watching a lot of videos on youtube. Do you recommend any specific resource(s)? Also, where can I find more mixtures questions besides on GMAT Club, do you know?

One gallon of soft drink is made of 40% orange juice and 60% water, ho [#permalink]

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29 Sep 2017, 10:42

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Hi nagu - I think genxer123 did a great job illustrating the problem. Nevertheless, here is my attempt to help you understand. Pardon my mess.

Attachment:

1.jpg [ 51.22 KiB | Viewed 855 times ]

Since Orange juice does not have any water in it (at least from the question's point of view), the percentage of water in orange juice is assumed to be 0. For ease, I will be using Water Proportion in my steps below. You could also use Orange juice to calculate the proportion. Using weighted average formula:

Proportion of Water in the resultant = \(\frac{(Proportion of Water in Soft Drink) (Volume of Soft Drink)+ (Proportion of Water in Orange Juice)(Volume of Orange Juice)}{ Volume of Soft Drink + Volume of Orange Juice}\)

the LHS represents the proportion of water in the final resultant mixture =>\(\frac{Water}{Total}\)= \(\frac{40}{100}\)

and the RHS represents

Proportion of water in the initial soft drink\(\frac{Water}{Total}\) = \(\frac{40}{100}\) * Volume of solution+Proportion of water in the orange juice\(\frac{Water}{Total}\) = \(\frac{0}{100}\) * Volume of solution

gmatclubot

One gallon of soft drink is made of 40% orange juice and 60% water, ho
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29 Sep 2017, 10:42